1. Field of the Invention
The present invention relates to an imaging device and a focusing method comprising a focus function which can be implemented in digital cameras.
2. Description of the Related Art
Conventionally, in imaging apparatus such as digital cameras, distance information to an object is detected and Auto-Focusing (AF) processing by a phase difference detection method of combining focus to an object based on this detected distance information is generally known. This phase difference detection method detects distance to an object from an image by which the image focus is formed by a pair of sensor arrays according to the principle of triangulation ranging.
However, in AF processing according to this phase difference detection method is affected by light and darkness of the photographing environment. Therefore, when the photographing environment is dark, the object distance cannot be detected correctly and a focused image cannot be photographed.
Accordingly, the conventional prior art disclosed in Japanese Laid-Open (Kokai) Patent Application No. 2003-075717 titled “DISTANCE DETECTING DEVICE” was developed. In this technology, namely, the size (the number of pixels) occupied by a person's face on the photographic image plane is calculated for every distance to the object which is tabulated as a table in advance and stored in a memory in a ranging/focusing circuit 30. This ranging/focusing circuit 30 correlates the focus of an object by extracting a person's face from an imaging signal at the time of ranging, counting the number of pixels corresponding to the extracted imaging signal, calculating the object distance from the above-mentioned table and driving a focus lens according to the calculated object distance.